chemistry 110 lecture unit 4 chapter 7-chemical...

Chemistry 110 Lecture Unit 4 Chapter 7-CHEMICAL REACTIONS, continued

A chemical reaction occurs when there is a change in chemical composition.

TYPES of REACTIONS: I. Double Replacement/Double Exchange/Metathesis Reactions

In an double displacement reaction, the positive end and negative end of compounds "change partners" to form new products: a. PRECIPITATION REACTIONS *Note: A ppt must form for the rxn to occur. (if it doesn't...Then NR!)

SOLUBILITY RULES FOR IONIC COMPOUNDS

Ion contained in the Compound

Solubility Exceptions

Group IA soluble

NH4+ soluble

C2H3O2- soluble

NO3- soluble

Cl-,Br-, and I- soluble Ag+, Pb2+, Hg22+

SO42- soluble Ca2+,Sr2+,Ba2+,Pb2+

CO32-, PO43-, CrO42- insoluble group IA and NH4+

S2- insoluble group IA,IIA, and NH4+

OH- insoluble group IA, Ca2+, Ba2+,Sr2+

a. PRECIPITATION REACTIONS, CONTINUED: b. ACID-BASE AND GAS EVOLUTION REACTIONS (Molecule formation)

(1) Neutralization- Acid + Base -> Salt + water

(2) A weak acid is formed

STRONG ACIDS HNO3 HClO4 H2SO4

HCl HBr HI

(3) A gas forms

a. H2CO3 decomposition to form CO2 (g) and H2O (l) b. H2S Formation

NET-IONIC EQUATIONS Net Ionic equations shows the species that are reacting in solution

Molecular equation - the bookkeeping equation

Total or complete ionic equation - Shows substances in their predominant form

Net-Ionic equation - Shows the only species that underwent a chemical reaction. [Spectator ions have been eliminated]

How to write net-ionic equations 1. Write a balanced equation (correct chemical formulas)

2. Write a total ionic equation: a. Write the following in the ionized form: Write As: Soluble Salt FeCl2(aq) Fe2+(aq) + 2Cl-(aq)

Strong Acid HCl(aq) H+(aq) + Cl-(aq) Strong Base NaOH(aq) Na+(aq) + OH-(aq)

b. Write the following in the molecular form: (1) Weak acids and weak soluble bases: H2CO3 HCN NH3(aq) (2) Insoluble ionic compounds AgCl(s), PbS(s), Fe(OH)2(s), CrCrO4(s) (3) Molecules H2O(l) H2(g) H2S(g) CO2(g) 3. Write the net-ionic equation by eliminating all spectator ions. (The unreacting species) The net-ionic equaiton must be in the simplest ratio possible

If all species on both sides are spectator ions g N.R. EXAMPLES: 1. Oxalic acid is poured into a solution of potassium hydroxide.

Molecular equation_______________________________________________________________________

Total ionic_____________________________________________________________________________

Net ionic____________________________________________________________________________

2. Solutions of Iron (II) chloride and cesium hydroxide are mixed together


Total ionic_____________________________________________________________________________

Net ionic____________________________________________________________________________

3. Sodium nitrate and cupric acetate solutions are mixed together.


Total ionic_____________________________________________________________________________

Net ionic____________________________________________________________________________

4. Chromium (III) hydroxide is slowly stirred into a solution of acetic acid.


Total ionic_____________________________________________________________________________

Net ionic____________________________________________________________________________

5. Aqueous sodium phosphate and sulfuric acid are mixed.


Total ionic_____________________________________________________________________________

Net ionic____________________________________________________________________________

6. lead (II) cyanide and potassium carbonate solutions are mixed


Total ionic_____________________________________________________________________________

Net ionic___________________________________________________________________________

II. Combustion, Synthesis, decomposition, and Displacement Types of Chemical

Reactions A. Combustion Reactions involves organic compounds: General Form: (CxHyOz) + O2(g) g CO2(g) + H2O(g) B. Synthesis/Combination Reactions - One product is formed: Know these specific cases!! 1. Metal + Nonmetal combines to form an Ionic compound ex. 2. Metal Oxide + H2O combines to form a Base ex. 3. Nonmetal Oxide + H2O combines to form an Acid ex.

C. Decomposition-A single reactant will form two or more products Know these specific cases 1. Carbonates (CO32-) decomposes to oxides and CO2(g) Ex.

2. Binary Ionic Compounds decomposes to Metal + Nonmetal 3. Decomposition of hydroxides to form a metallic oxide and water 4. Decomposition of chlorates to form chlorides and oxygen gas D. Single displacement Reactions/ Replacement Rxns. TYPES: Type 1: Metal + H2O g Base + H2(g) Type 2: Metal + Acid g Salt + H2(g) Type 3: Metal1 + Salt1 g Metal2 + Salt2 Type 4. Nonmetal1 + Salt1 g Nonmetal2 + Salt2

(HOH)

PREDICTING if the Single displacement reaction will occur USING: 1. Activity table for metals-for Single displacement types 1-->3

a. Which metals reacts with H2O

b. Which metals reacts with hot H2O, steam

c. Which metals reacts with acids

d. Which metals are more reactive

2. Activity series for halogens for single displacement type 4

Type 1. Metal + H2O g Base + H2(g) Type 2 Metal + Acid g Salt + H2(g) Type 3 Metal1 + Salt1 g Metal2 + Salt2 Type 4 Nonmetal1 + Salt1 g Nonmetal2 + Salt2

Examples 1. Zn(s) + H2O (g) g

2. Hg(l) + HNO3(aq) g

3. Ca(s) + HNO3(aq) g

4. Cu(s) + AlBr3(aq) g

5. Ag(s) + HCl(aq) g

6. Ni(s) + AlCl3 g

7. Cl2 + KI(aq) g

8. K + H2O g

9. Fe (s) + CuSO4 (aq)

Use For: Single Replacement Reactions ONLY!!! ACTIVITY SERIES FOR COMMON METALSACTIVITY SERIES FOR COMMON METALS

MOST ACTIVE

K Na Reacts with H2O(l) Ca Mg Al Mn Reacts with H2O(g), (Steam) Zn Cr Fe Ni Sn Pb H Cu Hg Ag Pt Au

LEAST ACTIVE *Note: Other types of rxns may occur with acids but will not produce H2

gas-you are not responsible to know these 'other' types

Reacts with Acids to

liberate hydrogen gas

*Do not react with Acids

to liberate hydrogen gas

III. Predicting, Writing and Balancing Chemical equations A. Items to be included: Correct prediction of products using and knowing: a. Reaction types b. Activity table c. Electron affinity d. Solubility rules e. Correct Chemical Formulas f. Diatomic elements g. Physical states **NOTE: IONIC COMPOUNDS IN AIR ARE SOLIDS B. Practice Problems:

1. Sulfuric acid + aluminum hydroxide

2. Calcium is added to water

3. Zinc + a solution of copper (II) chloride

4. Magnesium + chlorine

5. Sodium Carbonate is heated

6. Solutions of Iron (II) nitrate and sodium carbonate are mixed

Chapter 8-QUANTITIES IN CHEMICAL REACTIONS

STOICHIOMETRY The numerical relationship among the reactants and products in a balanced equation (Chemical reaction) I. The Balanced equation A balanced equation shows a chemical reaction in shorthand: For example: Two magnesium atoms (a solid) when ignited, reacts with oxygen atoms to form solid magnesium oxide The meaning of a balanced Chemical Equation: A bookkeeping system Example: The balanced equation - mole to mole ratios These mole to mole ratios are exact numbers.

II. The Stoichiometric Pathway:

# of particles of Known # particles of Unknown

Avo. # balanced equation Avo. #

Moles of Known Moles of Unknown

molar mass molar mass

Grams of Known Grams of Unknown III. Stoichiometric Calculations The reaction: Chromium metal is reacted with chlorine gas to produce chromic chloride Key: You must have a balanced equation!! a) How many moles of chromic chloride is made from 6.0 moles Cr? b) How many moles of chlorine gas is needed to react with 6.0 moles of Cr? c) How many grams of chromic chloride is made from 1.60 moles of chlorine gas? d) How many grams of Cr is needed to produce 36.0 g of chromic chloride

PR0BLEMS: 1. Octane or C8H18 (l) is a component of gasoline. If 35.0 mol O2(g) in the air is used to burn a

sample of octane completely. a. How many grams of carbon dioxide gas are produced? b. How many g of water are produced from 54.0 grams of octane.

2. A crucial reaction for the maintenance of plant and animal life is the conversion of oxygen gas to ozone gas[O3(g)] in the lower part of the stratosphere. How many molecules of oxygen gas are needed to produce 17.0 moles of ozone (O3)?

3. How many grams of oxygen gas are required for the complete combustion of 694 g of methane CH4(g) in a sample of natural gas?

4. The percent of aluminum in the compound Al2X3 is 18.56%. What is the molar mass of the element represented by X? 5. 75. 0 grams of iron are reacted in chlorine gas to produce 170.2 g the compound FeClx. What is the value of the integer x?

6.

IV. LIMITING REACTANTS When most reactions are performed, some of the reactants is usually present in excess of the amount needed. If the reaction goes to completion, then some of this excess reactant will be left-over. The limiting reactant is the reactant used-up completely and it "limits" the reaction. For example:

PROBLEMS: 1. Calcium hydroxide is reacted with nitric acid. a. How many moles of calcium nitrate is produced when 3 moles of calcium hydroxide and 4 moles of nitric

acid are mixed? How many moles of each product are formed? How much excess reactant is left-over? BALANCED EQUATION: What is the maximum moles of calcium nitrate formed? What is the limiting reactant?_______________ What is the excess reactant?__________________ How many moles of the excess reactant is left over?

Moles of calcium hydroxide leftover________________ Moles of nitric acid left over___________

Problem 2: 50.0 g of magnesium bromide and 100.0 g of silver nitrate are mixed. a. How many grams of precipitate are produced? b. How much excess reactant is left-over? BALANCED EQUATION: What is the maximum mass of precipitate formed? What is the limiting reactant?_______________ What is the excess reactant?__________________ How much of the excess reactant is left over? Mass of magnesium bromide leftover________________ Mass of silver nitrate left over___________

SOLUTION STOICHIOMETRY

# of particles of Known # particles of UNK.

balanced equation

g of Known Moles of Known Moles of UNK. g. of UNK.

Molarity (mol/L)

Vol. of Known Vol. of UNK. . (liters) (liters)

PROBLEMS: 1. HCl + AgNO3 g a. How many moles of AgCl(s) are produced from 30.0 mls of 0.10 M HCl?

b. How many mls of 0.10M HCl is needed to react to produce 17.0 g of AgCl?

2. 25.0 g of zinc are reacted with 1855 mls of 0.250 M hydrochloric acid. How many grams of hydrogen gas are produced? Zinc metal + hydrochloric acid g

3. How many milliliters of 0.500 M H2SO4 are required to neutralize 2.50 ml of 2.50 M LiOH?

4. If 25.0 ml of 0.150 M Ba(OH)2 is required to react completely with 45.0 ml HCl solution, what is the molarity of the HCl(aq)?

5. A soda acid (sodium hydrogen carbonate) fire extinguisher makes carbon dioxide by the reaction: NaHCO3(s) + H2SO4(aq) g Na2SO4(aq) + H2O (l) + CO2 (unbalanced)

Molar Masses are: MM-NaHCO3 =83.91 MM-H2SO4-98.07 MM-Na2SO4=141.84 MM-H2O= 18.01 MM-CO2 =44.01

a. How many mls of 2.50 Msulfuric acid is needed to produce 10.0 g of carbon dioxide

b How many mls of 2.50 Msulfuric acid are needed to react with 1.34 x 1030 units of sodium bicarbonate? 7. How many mls of 6.0 M hydrochloric acid are needed to react to produce 124 mls of hydrogen gas at 1.3

atm and 25oC

V. PERCENT YIELD The amount of product that has been previously calculated from chemical equations show the maximum yield (100%). However, many reactions fail to give a 100% yield of product. The theoretical yield is the calculated amount of product. The Actual yield is the amount of product actually obtained Actual Yield Percent Yield = X 100 Theoretical Yield Example: PROBLEMS:

1. 28.0 grams of nitrogen gas reacted with hydrogen gas to produce 26.0 grams of ammonia. What is the percent yield of the reaction?

2. How many grams of XeF2(g) will be produced when xenon reacts with 10.0 g fluorine gas and the percent yield for the reaction is 54%?

Deeper PROBLEMS 1. A 13.20 g sample of a mixture of CaCO3 and NaHCO3 was heated, and the compounds decomposed as

follows.

Ca CO3 à CaO + CO2 2 NaHCO3 à Na2CO3 + CO2 + H2O

The decomposition of the sample yields 4.35 g of CO2 and .873 g of H2O. What percentage, by mass, of the original sample was CaCO3?

2. Determine how many CoCl3 formula units can be produced from a reaction mixture containing 525 cobalt atoms and 525 HCl molecules according to the following reaction.

2 Co + 6 HCl à 2CoCl3 + 3 H

CHEM. 110

CLS PRACTICE EXAM 4 _________________________________________________________________________

100 POINTS-There are 5 pages to this exam SHOW ALL YOUR WORK. YOUR ANSWERS MUST HAVE THE CORRECT NUMBER OF SIGNIFICANT FIGURES AND UNITS. CORRECT SPELLING MUST BE USED. 1. A soda acid (sodium hydrogen carbonate) fire extinguisher makes carbon dioxide by the reaction:

NaHCO3(s) + H2SO4(aq) g Na2SO4(aq) + H2O (l) + CO2 (unbalanced) Molar Masses are: MM-NaHCO3 =83.91 MM-H2SO4-98.07 MM-Na2SO4=141.84 MM-H2O= 18.01 MM-CO2 =44.01

a. How many moles of H2SO4 are needed to react with 2.78 moles of NaHCO3? b. How many grams of CO2 are obtained when 1.37 moles of H2SO4 react? c. How many grams of NaHCO3 must react in order to produce 13.5 grams of Na2SO4. d. How many carbon dioxide molecules are produced from 155 mg of sodium bicarbonate? e. How many moles of sodium sulfate are produced when 177 g of water is formed?

2. Complete and balance the following reactions Correct chemical formulas and physical states

[(aq),(s),(l), and (g)] must be used: heat

a. CaO2 g b. C2H3OH liquid is burned c. Aluminum metal is added to a solution containing Plumbic nitrate d. Solid Manganese (III) oxide is carefully placed in erlenmeyer full of water e. Iron metal + aqueous silver nitrate g f. Solutions of sodium sulfide and zinc iodide are mixed heat g. K2CO3 g h. Al (s) + S8 (s) g i. Acetic acid is spilled on a tin can. j. Chlorine water is added to a ferrous bromide solution. k. Nickel (III) bromide is heated l. Zinc is dropped in a beaker of water m. Aluminum metal is placed in steam. n. The combustion of C4H10 gas

o. Cobalt metal + nitrogen gas g p. Sodium bromide (aq) + Manganese (II) nitrate (aq) g

3. The reaction:

3CCl4 + Cr2O3 g 2CrCl3 +3CCl2O

MM-CCl4=153.8 MM- Cr2O3=152.0 MM-CrCl3=158.4 MM-CCl2O=98.9

is used to make CrCl3. In one experiment 6.37 g of Cr2O3 was treated with excess CCl4 and yielded 8.75 g of CrCl3. Calculate the percent yield of CrCl3.

4 For the following reactions: a. Complete b. Balance c. Write the physical states for the reactants and products d. Write the net-ionic equations ***NOTE: All the following reactions occur in solut***NOTE: All the following reactions occur in solut ion (water!! ! ! ! !)ion (water!! ! ! ! !)

(1) Zinc acetate + lithium carbonate (2) Nickel (III) hydroxide + sulfurous acid g (3) Ammonium phosphate + Cobalt(II) bromide g (4) Hydrocyanic acid + Nickel (II) chloride g * Note: ionic compounds of CN- are soluble (5) Acetic acid + Barium hydroxide g (6) Sodium sulfate + Chlorous acid g

5. A volume of 54.6 ml of 0.100 M HCl solution is required to neutralize 34.0 ml of an NaOH solution of unknown molarity. What is the concentration of the NaOH solution? 6. Nitric oxide (NO) reacts instantly with oxygen gas to give nitrogen dioxide (NO2) , a dark brown gas. 4677 grams of oxygen gas is reacted with 6555 grams of NO:

O2(g) + NO (q) g NO2(g) [unbalanced]

MM-O2=32.0 MM-NO=30.0 MM- NO2=46.0

a) The limiting reactant is _________________.

b) How many kilograms of NO2 is produced?

c) How many kilograms of the excess reactant will remain after the reaction is completed?

7. Iron (III) oxide can react with aluminum metal to produce aluminum oxide and iron metal (hint: this is the chemical rxn!!) This is called the thermit reaction and it produces so much heat that it can be used for incendiary bombs and for welding. How many grams of aluminum oxide will be produced by the reaction of aluminum with 45.8 g of iron(III) oxide?

chemistry 110 lecture unit 4 chapter 7-chemical...

Documents